Method of and apparatus for cold working and expanding a metal member such as a channel stud



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METHOD OF AND APPARATUS FOR COLD WORKING AND EXPANDING Filed March 19, 1964 O@ mgm .www O N QOOOQOfOOQDOODDQD/BD OCCOOOOOCOOOOO NAN', \%m

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METHOD OF AND APPARATUS FOR COLD WORKING AND EXPANDING A METAL MEMBER SUCH As A CHANNEL STUD A Filed March 19, 1964 6 Sheetsmheet 2 ROBERT D. TERRELL.

Jan. 17, 1967 n. n TERRELI. ETAL 3,298,08

METHOD OF AND APPARATUS FOR COLD WORKING AND EXPANDING A METAL MEMBER SUCH AS A CHANNEL STUD Filed March 19, 1964 6 Sheets-Sheet 5 INVENTORS ROBERT DTERRELL BYJACK 0. ABNEY ATTORNEYS Jan. 17, 1967 R. D. TERRi-:LL ETAL 3,298,081

METHOD OF AND APPARATUS FOR COLD WORKING AND EXPANDING A METAL MEMBER SUCH AS A CHANNEL STUD Filed March 19, 1964 6 Sheets-Sheet 4 INVENTORS ROBERT D.TERRELL E,'YJACK G1. ABNEY ATTORN EYS w u e f kann M, MM5? R. D. TERRE-:LL ETAL mmm METMDD 0F AND MPARATUS FOR COLD WORKING AND EXPAMDING- A METAL MEMBER SUCH AS A CHANNEL STUD Filed March 19, i964 6 Sheets-511t 5 KNW ENT@ F25 RODERT D. TERRELL- BWI/MCM 0. ABMEY Jam.` 17, 1967 R. D. TERRELL ETAL 3,298,081

METHOD OF AND APPARATUS FOR COLD WORKING AND EXPANDING A METAL MEMBER SUCH AS A CHANNEL STUD Filed March 19, 1964 6 Sheets-Sheet 6 Q /Z 5g //f Of/ r n 2/ w ,575 //0 n w 2l lv \|I v LN l 14 Fl G. |15

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F l 5 @j INVENToRs /O ,I/Q/ ROBERT D. TERRELL ATTORNEYS United States Patent O 3,298,081 METHOD F AND APPARATUS FOR COLD WORK- ING AND EXPANDING A METAL MEMBER SUCH AS A CHANNEL STUD Robert Duval Terrell, Huntington, and Jack O. Abney, Vienna, W. Va., assignors to Penn Metal Company Inc., Boston, Mass., a corporation of Delaware Filed Mar. 19, 1964, Ser. No. 353,083 12 Claims. (Cl. 29-6.2)

The present invention relates to improvements in the process of fabrication `of expanded metal members such as channel studs, double studs, joists and Z sections in whole or in part by cold working and to apparatus for use in practicing such process. `Commercial steel (both hot and cold rolled), stainless steel, aluminum and other suitable metals may be used for the stock. y

Heretofore, such products have been made commercially by punching the web of a channel stud to form latticed members or strands and the metal punchings sold as scrap. For example, in case of a 3% inch hollow metal channel stud having 1/2 inch anges for non load 3,298,081 Patented Jan. 17, 1967 ice FIG. 5 is an enlarged sectional View of the apparatus elements for simultaneously and progressively cutting, bending and elongating a pair of strands to prepare them for lateral expansion in a later step in the process, the section being taken on the lines 5-5 of FIG. 6;

FIG. 6 is a side elevational View of the cutting, bending and elongating elements taken on the lines 6--6 of FIG. 5;

FIG. 7 is a view similar to FIG. 5, `but showing cutting, bending and elongating elements for forming a pair of elongated strands in the `web portion of a Z section;

FIG. 8 is a sectional view taken on the lines 8--8 of FIG. 9 showing the apparatus elements in one station of the lateral expanding unit, this unit being also shown in FIGS. 1, 3 and 4;

FIG. 9 is anenlarged plan view, with parts broken f away, showing certain of the apparatus elements of the bearing use made from commercial hot rolled steel stock, 1

about 45% of the metal is punched out as scrap and it sells for only about 1 per pound compared to the original cost of about 7q': per pound.

While attempts have been made to expand a web of a `channel stud laterally by cold working, by forming rows of slits in the web and then using stationary guides which operate on the anges to expand the slitted web while the strands formed between the slits are simultaneously passed between pressure rolls, they have not met with commercial acceptance, due primarily to the formation of cracks which weaken the metal at the junctions of the strands and the marginal web portions which adjoin the bases ofthe flanges.

One object of this invention is to provide a commercially acceptable method and apparatus whereby an elongated metal member may be formed and expanded in a continuous cold working process from a strip of metal without loss of metal in the form of scrap.

Another object is to provide a method of cold working and an apparatus for simultaneously and progressively cutting, bending and elongating a pair of strands connected together at their mid portions and connected to adjacent web portions at their ends to prepare them for lateral expansion without damage in a later expansion step in the method.

A yet further object is to provide a method of cold working and an apparatus for laterally expanding the slitted web of an elongate metal member by means of rolls without the use of stationary guides. Although the features of this invention which are believed to be novel are set forth in the appended claims, details as to its practice in preferred forms, as Well as further objects and advantages thereof, will be apparent to persons skilled in the art `by reference to the following description taken in connection with the accompanying drawings wherein:

FIG. l is a diagrammatic side elevational view of apparatus for performing the invention;

FIG. 2 is a plan View of a channel stud with its flanges down during its progressive formation by the apparatus of FIG. 1, this plan View being coordinated with the elevational view of FIG. l;

FIG. 3 is a series of diagrammatic partial transverse vertical sectional views of FIG. l taken upon the unnumbered section lines located above them in FIG. l;

FIG. 4 is a series of partial plan views, with parts in section, showing portions of the apparatus of FIG. l, coordinated with FIG. l, but with the metal workpiece omitted and taken generally on the lines 4 4 of FIG. 1.

unit for laterally expanding the slitted web of a channel stud;

FIG. l0 is a perspective, with some parts broken away and shown in section, taken from the back side of FIG. 1 and showing the apparatus elements for alternately raising and lowering the punch shoe of the press and for imparting step by step feed to the elongate metal work piece so as to advance it through the apparatus when the cutting, bending and elongating punches are out of engagement with the work piece;

. uct upon completion yof th-e simultaneous and progressive cutting, bending and stretching steps, but with the anges extending upwardly rather than downwardly so as to better sho-w the strands;

FIG. 13 is a sectional View of a Z section made by the process and apparatus of this invention;

FIG. 14 is a sectional view of a joist mad-e from a channel stud produced by the process and apparatus of this invention to which angle members have been spot welded to form a second pair of anges; and

FIG. l5 is a sectional view of a double stud made by spot welding together two channel studs made by the process and apparatus of this invention.

Referring to FIG. 1l, the channel stud shown therein comprises flanges 10 having side web elements 11 which are connected together by a series of strands 12, the strands 12 being connected by areas of metal 13 which are located between the ends of the openings 14. Side openings 15 are provided between the strands and the side web elements 11. While beads 16 are shown extending longitudinally of the strands for the purpose of reinforcing or stiifening them, they are optional and the strands may be flat and located in the plane of the web elements 11. Because `the beading step is not essential to the process or apparatus yof this invention, no apparatus elements for performing it are shown in the drawings.

Referring to FIGS. l-4, a coil 13 of strip metal 17 of the desired width and gauge is mounted on the spindle 19 of the decoiler which is provided with an adjustable brake (not shown) to prevent yover decoiling when the strip metal is moved intermittently step lby step through the subsequent method steps and apparatus elements.

The strip of Lmetal 17 passes from the decoiler between the combined forming and feed rolls 20-22 which have shafts 118 and 23 respectively and which are mounted for rotation in suitable bearings (not shown). One end of each shaft 118 projects into a gear box 21 and the gears (not shown in FIGS. l, 3 and 4) which Iare attached to such ends of the shafts 11S and driven intermittently from the crank pin of the punch press by a mechanism which 3 is 'shown in FIG. 10 and which will be described below.

As the strip of metal is fed step by step *between the rolls 20-22 it is formed into ch-annel shape of the desired width, -as shown in FIG. 3. The pressure of these forming and feed rolls upon the metal member 17 also feeds it forwardly.

While only three sets of forming and feed rolls 20-22 are shown, more sets may be used, depending upon the cross-section of the member to ybe formed and the width land gauge of the metal being run. For example, more rolls are needed to form a Z section than to form a channel stud, -as is well known to persons skilled in the art.

The elongate channel member formed by the rolls 20-22 is fed forwardly to the punch press 30, wh-ich, as shown, consists of two stations.

The first station comprises :an upper slitting punch 31 (FIGS. 1, 3 and 4) which is detachably secured to the punch shoe 100 (FIGS. 1, 2 and 10). The -cutting edge of the slitting punch acts against the edge of the lower die block 32 to shear one slit in a rst row of longitudinally spaced slits 34 which `are located substantially at the longitudinal centerline of the web of the channel. The lower die 32 is detachably secured to the die shoe 101. The die block 35 is also detachably secured to the die shoe 101. A stripper 36 is detachably secured by the block 37 to the die shoe 101. When each slit 34 is cut, the metal beneath the cutting edge of the slitting punch 31 is depressed slightly at one side of the slit, as shown in FIG. 3.

Referring to FIGS. 1, 2 and 10, the punch shoe 100 is guided in its vertical movements towards and away from the die shoe 101 by four guide pins 102 secured to the die shoe 101 and slidably lreceived in perforations in the punch shoe 100. Crank throws 105 and 106 are supported by spaced frame elements 107 and they carry the crank pin 108. The crank throws S-106 are rotated about axles 109 by motor M. The upper ends of the links 109 are pivotally mounted on crank pin 108 and their lower ends are pivotally secured to blocks 110 which are secured to the punch sh-oe 100. This mechanism functions to alternately raise and lower the upper punch shoe 100 relative to the lower die shoe 101 upon each revolution of the crank throws.

Referring to FIGS. 1 and l0, the upper end of link 111 is pivotally mounted on the crank pin 108 and its lower end is pivotally secured to one end of the clutch arm 112. The other end of clutch arm 112 'is secured to the ratchet clutch 113 which is operatively connected through gears (not shown) in the gear -box 114 to a gear (not shown) which is fast on the drive shaft 115. A series of bevelled gears 116 (only one is shown) are secured to the drive shaft 115 and they mesh with bevelled gears 117 (only one is shown) attached to the ends of shafts 118 of the forming and feed rolls 20, these gears being located in the gear box 21 (FIGS. 1 and 4). The operative connections to the ratchet clutch are such that the forming and feed rolls 20-22 are driven only when the slitting punch 31 is out of contact with the metal workpiece.

Referring to FIGS. 1, 3, 4 and l0, simil-ar bevelled gears (not shown) lare located in the gear box 205 adjacent to the back side ofthe upper width sizing and web flattening rolls 201. Bevelled gears (not shown) on the drive shaft 115 mesh with bevelled gears (not shown) which are secured to the back ends of the shafts 200 of the upper set of web flattening rolls 201 so that the rolls 201-202 cooperate with the forming and feed rolls 20-22 to move the metallic member forwardly step by step after each downward cutting stroke of the punch shoe 100.

Referring to FIGS. l-6, 10 and 12, the second station of the punch press 30 -comprises the combined cutting and bending punch `40 which is detachably secured to the punch shoe 100 and which 'is moved upwardly and downwardly by the punch shoe. The die block 42-42 consists Iof two spaced blocks which are secured to the die shoe 101 to form the recess 43 between them which receives the punch at the lower portion of its downward stroke. The lower end 44 `of the punch 40 is preferably connected with the diverging sides of the punch by -arcuate corners, as shown best in- FIG. 6, so as to avoid creasing or scoring the strands transversely when they are cut, bent and elongated, as described below. Strippers 45 are secured to the die shoe 101 by blocks 46.

Referring to FIGS. 1, 2, 3, 5 and 6 and l2, as the cutting and bending punch 40 is moved downwardly, its end 44 engages the web of the metal member, the punch progressively enters the recess 43 and its cutting edges progressively act against the inner upper edges of the die block 42-42 and simultaneously and progressively cut a pair of slits 47, 48, beginning Iat opposite sides of the area 13 which is between the ends of a pair of slits 34 in the first row of slits. The slits 47 and 48 ultimately form a second row of sl-its and a third row of slits which -are located on opposite sides of the first row of slits. As the punch 40 descends, it not only progressively cuts a pair of slits 47, 48 but it also simultaneously and progressively bends `and elongates the pair of strands 12 to a semi-elliptical shape so they project outwardly from the plane of the side web members 11-11 to form the stage product shown in FIG. 12 (this stage product is shown upside down in FIG. 12 for purposes `of better illustrating the bent, elongated strands 12). Because the slits 47-48 are simultaneously and progressively cut as the strands are simultaneously and progressively bent and elongated, the forces applied at the junctions 49 between the strands and side web members 11 are relatively small and do not weaken the metal at these junctions, whereby the formation lof cracks in the metal at these junctions are prevented both during this Istep and during the laterlateral expansion step.

Upon each upward stroke of the press, the slit and elongated strands, as well as the work piece, are fed Iforward lone step and so that a fresh portion of the web containing only the first row of slits 34-34 is positioned beneath the combined cutting and bending punch 40 in preparation for its next downward stroke.

Referring to FIGS. 1-4, 8 and 9, the stage product of FIG. 12 is next advanced step by step through the lateral expansion apparatus which comprises a series of nondriven expanding rolls 50 having shafts 51 mounted for free rotation in bearings (not shown) supported by the frame members 52. These frame members S2 are adjustably secured to the base plate 53 by bolts 54 which pass through elongate Vslots 55. This permits the widths of the entrance end and of the exit end of the lateral expansion apparatus to be adjusted to the width of the stage product entering and to the width of the stage product which leaves the lateral expansion 4apparatus respectively. As shown in FIGS. 3, 8 and 9, the outer sides of each successive pair of expanding rolls 50 are spaced a greater distance apart than the outer sides of the preceding pair and they engage the inner sides of the flanges 10 of the channel member and progressively move them greater distances apart.

Back up rolls 56 have their shafts 57 mounted for free rotation in bearings (not shown) supported by bars S8 which are supported in adjustably spaced relation above frame members 52 by bolts 59 so that the distance between the adjacent peripheries of the back up rolls 56 and the expanding rolls 50 may be varied to accommodate metals of different gauges. Back up means other than the r-olls 56, may be provided but we now prefer to use nondriven rolls so as to minimize friction with the outer web members 11.

The shafts of the rolls 60 are supported for rotation in bearings (not shown) in the U-shaped bar 61 (FIGS. 8 and 9) which is mounted on the base plate 53. As shown in FIGS. l and 3, the -shafts of these rolls `are mounted progressively higher from the entrance to the exit ends of the lateral expansion apparatus. The rolls `60 engage the.

lowermost portion of the downwardly extending semielliptical portion of the stretched strands as they pass through the expander and these rolls i60 progressively form the strands upwardly towards the plane of the side web portions 11, compare the three views in FIG. 3. Consequently, when the channel stud emerges from the last pair of expanding rolls 50, it has been expanded substantially to its desired width and the elongated strands have been returned very nearly to the plane of the side web members 11.

Upper back up rolls 65, shown in dot-dash in FIG. 8, may be provided to back up the rolls 60 if desired.

The channel stud is next passed through the width sizing and web iiattening rolls 201-202 which, as explained above, also function as feed rolls and are driven intermittently by the drive shaft 115 and bevelled gears (not shown) contained in the gear housing 205, These rolls flatten the strands, size the width of the channel and straighten the flanges, as shown in FIG. 3.

If the strands are to be formed with beads 12, the channel is next passed between a pair of beading dies (not shown) which are moved toward and away from each other intermittently to form the beads `while the channel is at rest between them. At the same time, the edges of the strands may be straightened by leads (not shown) on the upper beading die `which enter the openings between the strands and straighten their edges as the upper beading dies is moved downwardly.

If desired the channel may then be passed between a series of straightening rolls (not shown) to insure that it is of uniform camber and free from bow curvatures.

Finally, the channel is severed in the desired lengths by a standard cutoff apparatus.

Referring to FIGS. 7 and 13, a Z section 8) is shown therein. In FIG. 13, it is in its final expanded condition and in FIG. 7, it is formed into la stage product rwherein a pair of strands have been cut and bent and elongated into a semi-elliptical shape by the combined slitting, bending and elongating punch 49A and other apparatus elements which correspond to the apparatus elements shown in FIG. 5 for processing a channel stud. Similar numerals followed by the letter A have been applied to these apparatus elements in FIG. 7. The necessary apparatus elements for use in the other steps of the process for forming an expanded Z section will be apparent to persons skilled in the art from the foregoing description of the fabrication of a channel stud.

A joist S2 is shown in FIG. 14. It is formed by at taching the flanges 84 of the angle members 83 to the side Iweb portions 11 of an expanded metal st-ud by means of spaced spot welds 85.

A double stud 90 is shown in FIG. 15. It is formed by securing two expanded studs together by spot welds 91.

By using the method and apparatus of this invention, commercially acceptable metal members, such as channel studs and Z sections are formed and expanded from strip metal in a continuous cold working process lwithout the loss of any metal in the form of scrap. There has been a long felt need for this process and there have been many unsuccessful attempts to ll it.

It should be understood that the specific embodiments of this invention which are disclosed herein are of a descriptive rather than a limiting nature and that various changes, combinations, substitutions or modications may be effected in accordance with these teachings without departing in spirit or scope from the invention in its broader aspects.

We claim:

1. In a method of cold working and expanding an elongated metal member the steps of: cutting a first row of longitudinally spaced slits through said member substantially parallel to the longitudinal center line thereof, intermittently advancing said member and, when the member is stationary, simultaneously and progressively cutting slits in a :second row and a third row of longitudinally spaced slits, each pair of opposing slits in said second and third rows Ibeing substantially parallel to the longitudinal center line of said member and the mid portions of said pair of opposing slits being located at opposite sides of the area of metal 'which is between the adjacent ends of a pair of slits of the rst row of slits, and simultaneously `with said latter -cutting step progressively bending and elongating the strands as they are being cut between said opposing pair of slits in said second and third rows of slits into a semi-elliptical shape projecting outwardly from the plane of said member, thereby simultaneously and progressively cutting and elongating said strands while said member is stationary and thereafter expanding said metal member laterally in opposite directions from its longitudinal center line whereby said elongated strands are progressively returned substantially to the plane of said member.

2. The method of claim 1 which also comprises the step of forming flanges at opposite sides of said metal member and wherein said member is laterally expanded by advancing the member with its flanges in engagement with portions of the outer sides of successive pairs of longitudinally spaced expanding rolls, at least portions of the outer sides of each pair of expanding rolls being spaced a greater distance apart than the outer sides of a preceding pair, whereby the flanges are progressively moved greater distances apart.

3. In a method of cold working an elongated metal member the steps of: cutting `a first row of longitudinally spaced slits through said member substantially parallel to the longitudinal center line thereof, intermittently advancing said member between a cutting, elongating and bending punch and a die block having a `recess which, when the member is stationary straddles the adjacent end portions of a pair of slits in said first row of slits and the area of metal located between the adjacent ends of said slits, and, while the member is stationary simultaneously and progressively cutting a slit in a second row of longitudinally spaced slits and a slit in a third row of longitudinally spaced slits, each pair of opposing slits in said second `and third rows of slits being substantially parallel to the longitudinal center line of said member and the mid portions thereof being located at opposite sides of said area of metal and simultaneously with said latter cutting step progressively bending and elongating the strands which :are being formed between said pair of opposing slits in the second and third rows of slits into a semielliptical shape projecting outwardly in the same direction from the plane of said member in one direction, thereby elongating said strands, said latter cutting, elongating and bending operations being performed by causing relative movement between said cutting and bending punch and said die block recess while said metal member is at rest between the punch and die block.

4. The method of claim 3 which also comprises the steps of forming flanges at opposite sides of said metal member and laterally expanding the member after said simultaneous cutting and strand elongating steps by advancing the metal member with its flanges in engagement with at the least portions of the outer sides of successive pairs of longitudinally spaced expanding rolls, at least portions of the outer sides of each pair of expanding rolls being spaced a greater distance apart than the outer sdes of a preceding pair, whereby the flanges are progressively moved greater distances apart.

5. In a method of cold working and expanding an elongated metal member the steps of: forming flanges at opposite side-s of said metal member, cutting a plurality of rows of slits through the web of said member, each row having individual slits spaced therealong `with each end near the middle portion of the `respective individual slits in the next adjacent row, laterally expanding the web of said member by advancing the member with its flanges in engagement with portions of the outer sides of successive pairs of longitudinally spaced expanding rolls, at

7 least portions of the outer sides of each pair of expanding rolls being spaced a greater distance apart than the outer Sides of a preceding pair, whereby the flanges are progressively moved greater distances apart.

6. The ymethod of claim S which also comprises the step of pressing portions of the web into engagement with .the arcuate surfaces of said rolls as said member is being advanced in engagement with the portions of the outer sides of said rolls.

7. The method of claim S which also comprises the steps of bending and strengthening a. pair of strands to form them into a semielliptical portion projecting outwardly from the plane of said member prior to advancing the member to the expanding step, and, concurrently with the expanding step, advancing said semi-elliptical portion of said strands into engagementwith the arcuate surfaces of successive strand flattening rolls each of which has its arcuate surface closer to the plane of said web member than a preceding strand flattening roll, ywhereby the strands of said elliptical portion are progressively moved toward the plane of the web as the `web is progressively expanded.

8. An apparatus for cold Working an elongated metal member in combination, means for cutting a rst row of longitudinally spaced slits through said member substantially parallel to the longitudinal center line thereof, means for intermittently advancing said member step by step and reciprocating means for simultaneously and progressively cutting a slit in a second row of longitudinally spaced slits and a slit in a third row of longitudinally spaced slits Iwhen said member is stationary, each pair of opposing slits in said Second and third rows being substantially parallel to the longitudinal center line of said member and the mid portions of said pair of opposing slits being located at opposite sides of the area of metal which is between the adjacent ends of a pair of slits of the first row of slits, said latter cutting means also comprising means for progressively bending and elongating the strands as they are being cut between said opposing pair of slits in said second and third rows of yslits into a semi-elliptical shape projecting outwardly in the same direction from the plane of said member, thereby simultaneously :and progressively cutting, 'bending and elongating said strands While said member is stationary.

9. The apparatus of claim 8 which also comprises means for expanding said metal member laterally in opposite directions from its longitudinal center line whereby said elongated strands are progressively returned substantially to the plane of said member as it is expanded laterally. 1

10. The apparatus of claim 8 which also comprises means for forming anges at opposite sides of said metal member and means for laterally expanding the member after said simultaneous cutting, bending and elongating of said strands, said expanding means comprising successive pairs -of longitudinally spaced rolls, at least portions of the outer sides of each pair of expanding rolls being spaced a greater distance apart than the outer sides lof apreceding pair for engagement With the anges of said member as it is advanced, whereby the flanges are progressively moved greater distances apart.

l1. In apparatus .for cold working and expanding an elongated metal member, in combination means for forming flanges at opposite sides of said metal member, means for cutting a plurality of rows of slits through the web of said member, each row having individual slits spaced therealong with each end near the middle portion of the respective individual slits in the next adjacent row, means for laterally expanding the web of said member by advancing the member with its flanges vin engagement with portions of the outer sides of successive pairs of longitudinally spaced expanding rolls, at least portions of the outer sides of each pair of expanding rolls being spaced a greater distance apart than the outer sides of a preceding pair, whereby t'he flanges are progressively moved greater distances apart.

12. Apparatusaccording t'o claim 11 which also comprises the means for pressing portions of the web into engagement with the arcuate surfaces of said rolls as said member is being advanced in engagement with the portions of the outer sides of said rolls.

References Cited by the Examiner UNITED STATES PATENTS 1,747,138 2/1930 Kesslerv 29 6.1 1,796,146 3/1931 Gersman 29-6.1

3,034,197 5/1962 Watanabe 29 6.1

RICHARD H. EANES, JR., Primary Examiner. 

1. IN A METHOD OF COLD WORKING AND EXPANDING AN ELONGATED METAL MEMBER THE STEPS OF: CUTTING A FIRST ROW OF LONGITUDINALLY SPACED SLITS THROUGH SAID MEMBER SUBSTANTIALLY PARALLEL TO THE LONGITUDINAL CENTER LINE THEREOF, INTERMITTENTLY ADVANCING SAID MEMBER AND, WHEN THE MEMBER IS STATIONARY, SIMULTANEOUSLY AND PROGRESSIVELY CUTTING SLITS IN A SECOND ROW AND A THIRD ROW OF LONGITUDINALLY SPACED SLITS, EACH PAIR OF OPPOSING SLITS IN SAID SECOND AND THIRD ROWS BEING SUBSTANTIALLY PARALLEL TO THE LONGITUDINAL CENTER LINE OF SAID MEMBER AND THE MID PORTIONS OF SAID PAIR OF OPPOSING SLITS BEING LOCATED AT OPPOSITE SIDES OF THE AREA OF METAL WHIC IS BETWEEN THE ADJACENT ENDS OF A PAIR OF SLITS OF THE FIRST ROW OF SLITS, AND SIMULTANEOUSLY WITH SAID LATTER CUTTING STEP PROGRESSIVELY BENDING AND ELONGATING THE STRANDS AS THEY ARE BEING CUT BETWEEN SAID OPPOSING PAIR OF SLITS IN SAID SECOND AND THIRD ROWS OF SLITS INTO A SEMI-ELLIPTICAL SHAPE PROJECTING OUTWARDLY FROM THE PLANE OF SAID MEMBER, THEREBY SIMULTANEOUSLY AND PROGRESSIVELY CUTTING AND ELONGATING SAID STRANDS WHILE SAID MEMBER IS STATIONARY AND THEREAFTER EXPANDING SAID METAL MEMBER LATERALLY IN OPPOSITE DIRECTIONS FROM ITS LONGITUDINALLY CENTER LINE WHEREBY SAID ELONGATED STRANDS ARE PROGRESSIVELY RETURNED SUBSTANTIALLY TO THE PLANE OF SAID MEMBER. 